The use of remote wireless telephone handsets in wire line telephone service systems is well-known. The remote handsets typically operate on RF channels below 50 MHz at power levels below 100 mw. These instruments are sold in numerous retail store outlets and require no FCC frequency assignment. Accordingly, they usually fall on or near the same RF channel frequency, especially if they are manufactured and provided from a single supplier.
As a result, an interference problem typically occurs between remote handsets and tends to degrade the service provided in proportion to the number of remote handsets operating in a given service area. A further interference problem exists in that the normally operating services in these frequency bands, i.e., TV, police, CB, utilities, etc., because of their higher power and larger populations, can render the remote sets virtually useless. Thus, the use of remote handsets in conjunction with a host subscriber unit in a wireless cellular radio telephone system has up until now been assumed difficult to accomplish, in view of interference problems such as those above described with respect to the wireless remote handsets used in the context of wire-line systems.
Accordingly, although three tiered cellular radio telephone systems are well known, such as that disclosed in U.S. Pat. No. 3,906,166 to Cooper et al, a four tiered system using wireless remote handsets has up until now not been feasible.